Department of Systems Neurophysiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
Department of Animal Model Development, Brain Research Institute, Niigata University, 1-757 Asahimachi, Niigata, 951-8585, Japan.
Brain Struct Funct. 2020 Mar;225(2):621-638. doi: 10.1007/s00429-020-02025-6. Epub 2020 Jan 18.
The cerebellar cortex has dual somatotopic representation, broadly in the anterior lobules and narrowly in the posterior lobules. However, the somatotopy has not been well understood in vermal lobule VIII, located in the center of the posterior representation. Here, we examined the axonal projections and somatosensory representation of the midline area of vermal lobule VIII in mice, using the striped zebrin expression pattern as a landmark of intra-lobular compartmentalization. Retrograde tracer injection into this area (zebrin stripes 1+ and 1- in lobule VIII) labeled neuronal clusters, bilaterally, in the pericanal gray matter (Stilling's nucleus) in the sacral spinal cord. Spinocerebellar axons labeled by biotinylated dextran amine injection into the sacral pericanal gray matter terminated bilaterally in stripes 1+ and 1- in lobule VIII, with more than 70 terminals per axon, and the vermal stripes in lobules II-III. Dorsal flexion of the tail and electrical stimulation of the sacral spinal gray matter elicited the firing of mossy fiber terminals in stripes 1+ and 1- in lobule VIII. Anterograde labeling of Purkinje cell axons in this area showed terminals in the medial pole of the medial cerebellar nucleus. Lesioning of this area impaired locomotor performance in the rotarod test. These results demonstrated that stripes 1+ and 1- in lobule VIII receive tail proprioceptive sensation from the Stilling's nucleus as their predominant mossy fiber input. The results also suggest that locomotion-related activity is represented not only in the anterior lobule, but also in lobule VIII in the cerebellar vermis.
小脑皮层具有双重躯体定位，广泛存在于前叶，狭窄存在于后叶。然而，蚓部VIII 小叶位于后叶代表区的中心，其躯体定位尚未得到很好的理解。在这里，我们使用条纹棘蛋白表达模式作为小叶内隔室化的标志，研究了小鼠蚓部 VIII 小叶中线区域的轴突投射和体感代表。将逆行示踪剂注射到该区域（VIII 小叶的条纹 1+和 1-），双侧标记了在骶髓近管灰质（斯蒂林核）中的神经元簇。将生物素化葡聚糖胺注射到骶骨近管灰质中标记的脊髓小脑轴突双侧终止于 VIII 小叶的条纹 1+和 1-，每个轴突有超过 70 个末端，以及 II-III 小叶的蚓部。尾巴的背屈和骶骨脊髓灰质的电刺激引起了 VIII 小叶条纹 1+和 1-中苔藓纤维末端的放电。该区域浦肯野细胞轴突的顺行标记显示在小脑中间核的内侧极有末端。该区域的损伤损害了旋转棒试验中的运动表现。这些结果表明，VIII 小叶的条纹 1+和 1-从前庭核接收尾巴本体感觉作为其主要的苔藓纤维输入。结果还表明，与运动相关的活动不仅存在于前叶，也存在于小脑蚓部的 VIII 小叶。
